<title>Statistical multiplexing of VBR MPEG sources under credit-based flow control</title>

Abstract

Due to statistical multiplexing in ATM networks, a large number of cells may be lost during the periods of network congestion. It is a common perception that feedback congestion control mechanisms do not work well for delay sensitive applications such as video transfer. The proposed approaches to avoid congestion in video applications are mainly based on constant bit-rate transmission. However, these schemes impose a delay in the order of a frame time. Besides, the network utilization is reduced since bandwidth allocation at peak rate is necessary. Variable bit rate (VBR) coding of video signals is more efficient both in terms of coding delay and bandwidth utilization. In this paper, we demonstrate that using credit-based flow control together with a selective cell discarding mechanism, VBR video signals coded according to the MPEG standard can be statistically multiplexed with a very high efficiency. Both cell delay and cell loss guarantees can be made while achieving a high network utilization. A throughput of up to 83 percent has been achieved with a cell loss rate of under 10<SUP>-5</SUP> and maximum end-to-end cell queuing delay of 15 milliseconds in the statistical multiplexing scenarios under consideration. Since credit-based flow control works well for data applications, its successful deployment for video applications will pave the way for an integrated congestion control protocol.